As shown in FIG. 1, a conventional cooling structure includes a base 10 having an containing space 12 surrounded by a side wall 11 on a periphery thereof, an impeller and a stator set (not shown in FIG. 1, as the driving relationship between the impeller and the stator set is irrelevant to the subject of the present invention, both parts are not further depicted here), a shaft tube 13 disposed in the containing space 12, assembled or integrally formed on the base 10, providing a center bore for accommodating a bearing that supports a spindle of the impeller to rotate therein.
Whereas, when the base of the conventional cooling structure is formed by injection molding or die-casting, it is easily subjected to a contracted intrinsic stress and deformed, thus resulting in the following drawbacks;
slanted shaft tube: Depending on the position away from a sprue gate, regardless of a base formed by injection molding or die-casting, cooling time and temperature associated with a position of the base vary place by place. Hence, non-uniform contraction stresses arises from such difference, and the base of the conventional cooling structure is easily prone to a deformation resulting from the non-uniform contraction stresses, which gives rise to an oblique center line of the shaft tube.
large rotational run-out of impeller and large noise: As the base of the conventional cooling structure is easily subjected to the effect of the contraction stress, the shaft tube tends to be deflected and slanted. When the spindle of the impeller is supported by the central bearing inside the shaft tube, the impeller also exhibits a slanted condition. Consequently, when the impeller rotates, the slanted angle will make the impeller generate serious run-out, which also accompanies with a wind shear effect to generate enormous noise.
high product defective rate: When the impeller, because of the slanted shaft tube, generates serious run-out and enormous noise, the most direct impact is certainly a significant increase of product vibration and noise test value that sometimes even exceed a standard value range and thus result in a higher product defective rate.
short lifespan: When the impeller of the cooling structure is positioned in an environment with high run-out and high vibration amplitude for a long period of time, the life duration of the structure itself could be worn out seriously. Above all, the spindle and the bearing will be worn out much faster for withstanding the run-out and thus shorten the lifespan of the cooling structure.
As a consequence, to completely tackle the issue intrinsic to the above-mentioned conventional structure, a base design of cooling structure with a brand new idea must be aggressively conceived and developed to take both the quality and the lifespan of the product into account.